Quick questions on Galvanic cells, fuel cells and cell EMF: VCE Chemistry Unit 3

7short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is calculating cell EMF?

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The EMF (or cell potential) E°_cell is the voltage the cell delivers under standard conditions (1 mol L^-1 solutions, 25°C, 1 atm for gases).

What are primary cells?

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The redox reaction is one way. Once the reactants are consumed, the cell is dead and discarded. Cheap, simple, used in low-drain applications (remote controls).

What are secondary cells?

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The redox reaction is reversible. Applying an external voltage in reverse drives the reaction backwards, regenerating the original reactants. Higher initial cost, but cheaper per use over the cell's life.

What are fuel cells?

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A continuous supply of fuel (e.g. H2) and oxidant (O2) enters the cell. The cell runs as long as the supply continues.

What is q1?

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Sketch and label a galvanic cell using

\text{Zn} | \text{Zn}^{2+}

and

\text{Cu} | \text{Cu}^{2+}

electrodes. State the polarity of each electrode. [4 marks]

What is q2?

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Calculate the EMF and identify the spontaneous direction for a cell built from

\text{Fe}^{2+} | \text{Fe}

(

E^{\circ} = -0.44 \, \text{V}

) and

\text{Ag}^+ | \text{Ag}

(

E^{\circ} = +0.80 \, \text{V}

). [3 marks]

What is q3?

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\text{Mg} | \text{Mg}^{2+}

(

E^{\circ} = -2.37 \, \text{V}

) and

\text{Cu} | \text{Cu}^{2+}

(

E^{\circ} = +0.34 \, \text{V}

) cell operates for

30 \, \text{minutes}

0.20 \, \text{A}

. (a) Calculate the EMF. (b) Calculate moles of

\text{Mg}

consumed.

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